Extruding without breaking edge loop
Here is how you make a keyhole with all vertices connected.

1) Create a circle (say 32 vertices)
Stay in Edit Mode  

2) Create a plane (also with 32 vertices)
Both the circle and the plane are a part of one object now.

3) Select both loops and connect them with Edge->Bridge Edge Loops
4) Almost done. All inner vertices are now connected into one loop.
5) You can now model you keyhole.

Summary: Edge loops work. It’s all quads.